Research for internal state of a volcanic conduit based on volcanic tremors, long-period earthquakes, and infrasonic signals

基于火山颤动、长周期地震和次声信号的火山通道内部状态研究

基本信息

批准号：
22540431
负责人：
TAKEO Minoru
金额：
$ 2.75万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2010
资助国家：
日本
起止时间：
2010 至 2012
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-22540431/
关键词：
火山現象数理モデル実験火山地震微動空振

项目摘要

The purpose of this research is estimation of eruption style variation establishing a new method relating to oscillation data and an internal state of a shallow part of a conduit. During the early period of volcanic activity at the Shinmoe-dake volcano in 2011, various kinds of activities, such as sub-Plinian eruptions, a magma effusion, and Vulcanian eruptions, occurred sequentially. We succeeded in obtaining multi-items data, such as broadband seismograms, tilt motions, and infrasonic signals, nearby the summit crater during these three different eruption styles. In the Vulcanian stage, almost all Vulcanian eruptions were preceded by trapezoidal inflations followed by various time sequences of tilt motions, which became increasingly more complicated throughout the frequent Vulcanian eruptions. In spite of the complicated time sequences of the preceding inflations, we have found clear linearity between the preceding duration versus elapsed time. These observations can be consistently explained based on the assumption that a Vulcanian eruption is induced by a catastrophic rupture of the strongest closed, solid magma frame in a conduit due to magma degassing overpressure, and the degassing from the magma declines exponentially with time. Switching between seismic-only harmonic tremor and seism-acoustic harmonic tremor has been reported during Shinmoe-dake eruptionactivity. Switching was simulated in a laboratory experiment. At lower fluid stiffness, a stable, open conduit was produced, and the harmonic signals generated within the experimental apparatus were efficiently transmitted into the atmosphere. We established a simple method to distinguish infrasonic signals from wind noise, demonstrating that it effectively detects not only main eruptions, but also minor activity generating weakinfrasound hardly visible in the wave traces.

这项研究的目的是估计喷发样式变化，该变化建立了一种与振荡数据有关的新方法和导管的浅层部分的内部状态。在2011年Shinmoe-Dake火山的火山活动的早期，依次发生了各种活动，例如次型爆发，岩浆积液和Vulcanian喷发。在这三种不同的喷发样式期间，我们成功地获得了多项目数据，例如宽带地震图，倾斜动作和室内信号。在瓦肯尼亚阶段，几乎所有的瓦肯尼亚爆发均在梯形膨胀之前，随后是各种倾斜运动的时间序列，在整个频繁的瓦肯尼人爆发中，倾斜运动序列变得越来越复杂。尽管有前期通胀的复杂时间序列，但我们发现前持续时间与经过的时间之间的线性明显。这些观察结果可以基于这样的假设来始终如一地解释，即瓦基尼喷发是由由于岩浆脱气过压而导致的最强封闭，固体岩浆框架的灾难性破裂，而岩浆脱气的脱气随着时间而逐渐下降。在Shinmoe-Dake喷发性期间，已经报道了仅在地震的谐波和地震声音谐波之间切换。在实验室实验中模拟了切换。在较低的流体刚度下，产生了稳定的开放导管，并有效地传播了实验设备中产生的谐波信号。我们建立了一种简单的方法来区分红外信号和风噪声，表明它不仅可以检测到主要喷发，而且还可以在波形痕迹中几乎看不见弱膜片。